Enhanced Electrochemical Properties and Optimized Li+ Transmission Pathways of PEO/LLZTO-Based Composite Electrolytes Modified by Supramolecular Combination

Poly(ethylene oxide) (PEO) and Li 6.75 La 3 Zr 1.75 Ta 0.25 O 12 (LLZTO)-based composite polymer electrolytes (CPEs) are considered one of the most promising solid electrolyte systems. However, agglomeration of LLZTO within PEO and lack of Li + channels result in poor electrochemical properties. Herein, a functional supramolecular combination (CD-TFSI) consisting of active β-cyclodextrin (CD) supramolecular with self-assembled LiTFSI salt is selected as an interface modifier to coat LLZTO fillers. Benefiting from vast H-bonds formed between β-CD and PEO matrix and/or LLZTO, homogeneous dispersion and tight interface contact are obtained. Moreover, 6 Li NMR spectra confirm a new Li + transmission pathway from PEO matrix to LLZTO ceramic then to PEO matrix in the as-prepared PEO/LLZTO@CD-TFSI CPEs due to the typical cavity structure of β-CD. As a proof, the conductivity is increased from 5.3 × 10 −4 S cm −1 to 8.7 × 10 −4 S cm −1 at 60 °C, the Li + transference number is enhanced from 0.38 to 0.48, and the electrochemical stability window is extended to 5.1 V versus Li/Li + . Li‖LiFePO 4 CR2032 coin full cells and pouch cells prove the practical application of the as-prepared PEO/LLZTO@CD-TFSI CPEs. This work offers a new strategy of interface modifying LLZTO fillers with functional supramolecular combination to optimize PEO/LLZTO CPEs for solid lithium batteries.